1. Field of the Invention
This invention relates generally to current regulators and, more specifically, to a telephone loop-current regulator which plugs into a standard telephone jack ahead of any terminal telephone equipment and which protects the terminal telephone equipment from high telephone-line loop-current and the damage or dysfunction that the heat produced from the excess power may cause the terminal telephone equipment.
2. Description of the Prior Art
As shown in FIG. 1, originally, telephone line current was limited only by the resistance on the telephone wires or "loop resistance". Because of Federal Communications Commission (FCC) and Bell Telephone Systems specifications for off-hook current load for terminal telephone equipment, the power generated in any piece of terminal telephone equipment may reach nearly two (2) watts. This amount of wattage is too much for most pieces of terminal telephone equipment to handle. This is especially true for newer solid-state terminal telephone equipment pieces such as Personal Computer (PC) cards and Personal Computer Memory Card International Association (PCMCIA) modems which are more likely to be susceptible to damage due to excessive power.
Recently, loop-current attenuators, FIG. 2, have been designed to limit telephone line current. Loop-current attenuators are devices which are manually adjusted to control the telephone line current using a selection of resistors and capacitors. While loop-current attenuators do work, there are several problems associated with them. First, loop-current attenuators must be adjusted when they are installed. This requires special testing equipment and technical training. Second, loop-current attenuators must remain in a fixed location or be constantly readjusted. They must also be readjusted if the terminal telephone equipment is changed which could occur anytime a user plugs in or unplugs a telephone or other terminal telephone device into the telephone jack. This severely limits the use of loop-current attenuators. However, the main problem with loop-current attenuators is the fact that no loop-current attenuator complies to FCC Regulations, Part 68, Section 68.314(c) (2) which limits the decrease in loop-current to no more than twenty-five percent (25%) from its peak during the first five seconds after the terminal telephone equipment goes off-hook. This is due to the capacitors which loop-current attenuators use to pass AC signals.
Therefore, a need existed to provide a portable loop-current regulator. The loop-current regulator must be easy to installed. The loop-current regulator must not require a user to have special testing equipment or technical training when installing the loop-current regulator. The loop-current regulator must not require the user to constantly readjust the loop-current regulator. The loop-current regulator must also comply to FCC Regulations, Part 68, Section 68.314(c)(2) which limits the decrease in loop-current to no more than twenty-five percent (25%) from its peak during the first five seconds after the terminal telephone equipment goes off-hook.